Effects of transcranial theta-burst stimulation on acute pain perception.

Transcranial stimulation of the primary motor cortex (M1) for the treatment of pain has attracted much interest in recent years. Non-invasive low frequency and high frequency repetitive transcranial magnetic stimulation (rTMS) over the M1 was reported to reduce both experimentally induced acute and chronic pain. In this paper we summarize the results of several studies from our laboratory and report the antinociceptive effects of a special rTMS paradigm, theta-burst stimulation (TBS). We have applied excitatory (iTBS) and inhibitory (cTBS) paradigms over two cortical locations (M1 and the primary somatosensory cortex (S1)). As evaluation criteria a pain rating scale and the recording of laser evoked potentials (LEPs) were used. Reduced subjective pain perception after cTBS could be objectified by alterations of LEPs that reflect pain related activations in the pain processing in the operculo-insular and anterior cingulate cortex. The stimulation of S1 had physiological effects (LEPs), but did not induce significant reduction in acute pain perception. We believe that the application of cTBS over M1 in pain research has a great potential and as a method it can contribute to a more efficient manipulation of the brain plasticity for therapeutic purposes, for example in chronic pain. Nevertheless, the effectiveness of other types of TBS paradigms should also be tested.